Halogenated butyl rubber of improved scorch characteristics

ABSTRACT

The scorch characteristics of halogenated butyl rubber compounds are improved by the addition of one of or a mixture of the free acid or the magnesium, aluminum, calcium or barium salts of oligomers of linoleic acid.

United States Patent 1191 Feniak Dec. 23, 1975 HALOGENATED BUTYL RUBBER 0F IMPROVED SCORCH CHARACTERISTICS [56] References Cited [75] Inventor: George Feniak, Wyoming, Canada UNITED STATES PATENTS 3,629,171 12/1971 Kremer et al. 260/23.7 B [73] Asslgnee' Polysar Samla Canada 3,630,974 12/1971 Ladocsi et a1. 260/5 [22] Filed: Nov. 22, 1974 [21] Appl No: 526,252 Primary Examiner-Murray Tillman Asszstant ExammerArthur H. Koeckert Related Appllcatlon Data Attorney, Agent, or FirmStevens, Davis, Miller & [62] Division of Ser. No. 408,542, 0m. 23, 1973, Pat. No. Mosher 30 F A P D [57] ABSTRACT orelgn pp omy am The scorch characteristics of halogenated butyl rubber Nov. 24, 1972 Canada 157388 compounds are improved by the addition f one f or a mixture of the free acid or the magnesium, alumi- 52 us. (:1. 260/5; 260/889; 260/890 a1 b us of on 0mm of nucleic [51] Int. 01. ..c0s1)9/04;c0s c 11/34 anum g [58] Field of Search... 260/23.7 H, 85.3 H, 23.7 M,-

10 Claims, No Drawings HALOGENATED BUTYL RUBBER'OF IMPROVED SCORCH CHARACTERISTICS This is a division of application Ser. No. 408,542, filed Oct. 23, 1973, now U.S. Pat. No. 3,880,821.

This invention relates to the stabilization of halogenated butyl rubber against premature cross-linking during compounding.

Halogenated butyl rubbers are fast curing and, as a result, their compounds tend to be susceptible to premature vulcanization when part or all of the curing ingredients are present and before all of the fabrication and shaping stages have been completed. When such premature vulcanization takes place, the compounds become tough and unworkable. Premature vulcanization is commonly referred to as scorching. The problem can be reduced by the use of certain scorch retarders. However, up to the present, the known scorch retarders are not entirely satisfactory in providing adequate time for processing or compounding in the production of the final shaped articles.

It is an objective of this invention to provide vulcaniz-. able halogenated butyl compounds having improved scorch characteristics.

It has now been discovered that vulcanizable compositions comprising halogenated butyl have longer scorch times when a scorch retarding agent selected from at least one of the free acid and the magnesium, aluminum, calcium or barium salts of an oligomer of linoleic acid is incorporated into the composition.

The term butyl rubber as employed herein is intended to refer essentially to a vulcanizable rubbery copolymer containing from'about '85 to 99.5% combined isoolefin having from 4 to 8 carbon atoms and 0.5 to 15% combined conjugated diolefin having from 4to 8 carbon atoms. Such copolymers and their preparation are well known in the industry. The isoolefin, such as isobutylene, is mixed with a conjugated diolefin, such as butadiene or isoprene, and an inert diluent selected from C to C aliphatic alkenes and chlorinated hydrocarbons such as methyl chloride, ethyl chloride, methylene chloride and ehtylene dichloride. The monomers may form from 10 to 50% by weight of the total monomer/diluent mixture. The mixture is polymerized in a reactor at a temperature in the range from about 0C to about l65C using cationic catalysts well known in the art. The polymerization reaction proceeds rapidly to produce a copolymer in the form of a slurry in the diluent.

The preferred copolymer which is used to produce the halogenated butyl rubber of this invention is a copolymer of isobutylene and isoprene, preferably having an isobutylene content of from 97 to 99.5 weight per cent, most preferably from 98 to 99 weight per cent, and an isoprene content of from 0.5 to 3 weight per cent, most preferably from 1 to 2 weight per cent. The halogenated butyl rubber contains chlorine or bromine in an amount from about 0.5 to about weight per cent. It contains not more than one atom of chlorine or not more than three atoms of bromine per double bond present in the original copolymer and preferably it contains from 0.5 to 2 weight per cent of chlorine or from 0.5 to 5 weight per cent bromine. Most preferably the halogenated polymer is a brominated butyl rubber containing from 1.5 to 2.5 weight percent bromine. The butyl rubber may be halogenated by means well known in the art. The solid rubber may be reacted on a hot rubber mill with a compound which releases halogen such as nitrogen halo-succinimide and nitrogen halo-hydantoin. Alternatively, the butyl rubber'may be dissolved in an inert hydrocarbon solvent such as pentane, hexane or cyclohexane and halogenated by addition to the solution of elemental chlorine or bromine and the halogenated butyl recovered therefrom.

Halogenated butyl rubbers may be used in various applications where rubbers are generally used and are particularly useful in applications involving adhesion to, or covulcanization with, more highly unsaturated rubbers such as natural rubber and synthetic unsaturated rubbers selected from polyisoprene, polybutadiene, styrene-butadiene polymers and ethylenepropylene-diene polymers.

The scorch retarding agent used in this invention is at least one of the free acid or the magnesium, aluminum, calcium and barium salts of an oligomer of linoleic acid. Linoleic acid is an organic monocarboxylic acid compound containing two carbon-carbon double bonds. It is well known in the art that this compound will undergo oligomerization particularly to form the dimer and the trimer. Such oligomerization is achieved by the action 'of heat, optionally in the presence of a catalyst, to yield a compound thought to be, for the dimer, a tetra-substituted cyclohexene having two carboxyl groups and one carbon-carbon double bond external to the cyclohexene ring. Preferred oligom'ers of linoleic acid are the dimer and the trimer. Salts of the dimeric or trimeric acid may be readily formed such as by reacting the acid with aqueous potassium or sodium hydroxide to yield a water soluble compound which may then be reacted with an aqueous solution of, for example, calcium chloride to yield the corresponding calcium salt.

The quantity of scorch retarding agent required to give the degree of scorch retardation desired will depend on the type and amount of other materials present in the vulcanizable composition. Generally, the quantity of scorch retarding agent is in the range of from about 0.5 parts to about 5 parts by weight per parts by weight of the polymeric component, i.e. the total quantity of rubber, in the vulcanizable composition. Preferably the amount of scorch retarding agent is from 0.75 to 2.5 partsby weight per 100 parts by weight of the polymeric component of the vulcanizable composition.

The vulcanizable composition of this invention may contain, in addition to the halogenated butyl and scorch retarding agent, other unsaturated rubbers and conventional compounding ingredients such as carbon black, other fillers, oil, wax, antioxidant, and other processing aids. Other unsaturated rubbers include natural rubber and synthetic unsaturated rubbers selected from polyisoprene, polybutadiene, styrenebutadiene polymers and ethylene-propylene-diene polymers. The polymeric component of the vulcanizable composition thereby is halogenated butyl and may optionally contain at least one of the aforesaid unsaturated rubbers. The halogenated butyl forms at least 20 per cent by weight and up to 100 per cent by weight of the polymeric component. The quantity of conventional compounding ingredients contained in the vulcanizable composition will depend on the use for the final shaped article and may be varied as well known in the art. The quantity of carbon black in the composition will generally be in the range of from 20 parts by weight to 100 parts by weight per 100 parts by weight 3 of the polymeric components.

The vulcanizable composition is vulcanized, on heating for a period of time, by reaction with zinc oxide, as for compositions containing halogenated butyl as the only polymeric component, or with sulphur or sulphur compound vulcanization agents alone or in combination with zinc oxide as when the polymeric component is halogenated butyl alone or in admixture with at least one other unsaturated rubber.

The vulcanizable composition is produced by mixing the halogenated butyl rubber with the scorch retarding agent. The process whereby the rubber and scorch retarding agent are mixed may be by dry state mixing or it may be by mixing in an aqueous phase. When the mixing is in the dry state, dry halogenated butyl and the dry retarding agent are mixed by a rubber compounding means such as in Banbury material mixer or on a rubber mill under conditions well known in the art and normally used for mixing such halogenated butyl rub ber with compounding ingredients. The scorch retarding agent may be mixed with the halogenated butyl as a separate step in the compounding process or may be mixed together with other compounding ingredients. When aqueous phase mixing is used, the halogenated butyl may be recovered from the halogenation reaction as a slurry in water and an aqueous solution of the scorch retarding agent may be mixed with said slurry, the halogenated butyl mixed with the scorch retarding agent being recovered therefrom and dried.

The invention is illustrated by the following examples, the scope of the invention not being limited thereto.

EXAMPLE 1 Using a Banbury mixing procedure, with the rotor running at 77 rpm, the rotor and gates at 215F and steam and water to the Banbury both off, the following compound was mixed for a total mixing time of minutes, the quantities being parts by weight:

4 Using 200g portion, the additives shown in Table I were incorporated, using the.mill mixing procedure given above. Scorch times for the compounds and stressstrain properties of the vulcanizates, which had been vulcanized for 30 minutes at 165C, were then determined.

The bromobutyl used was a commercial sample containing 2.1 weight per cent of bromine and having a Mooney (ML 1 12 at 125C) of 42. The carbon black used was a general purpose furnace black, the paraffinic oil is a petroleum oil having a specific gravity of 0.88 and a Saybolt Universal viscosity of 350 seconds at 80F, the tackifier resin used was a product of Rohm & Haas sold under the tradename Amberol ST- 149 and the alkyl phenol disulphide was a product of Pennwalt Chemical Corporation sold under the tradename Vultac 5. The calcium salt of the dimer acid was prepared as follows: 57g of linoleic acid dimer (Empol Dimer Acid 1022, obtained from Emery Industries Inc.) was added to a stirred solution of 10g NaOH in 500 ml of water. The reaction mixture was stirred and heated on a hot plate. When the temperature had reached about 60C, the mixture became very viscous and was then poured into a stirred solution of 28g of CaCl in 200 ml of water. The resultant pale yellow slurry was stirred and heated to about 80C for 15 min., collected by filtration, washed thoroughly with water and air dried. The product was an off-white powder. The scorch time was determined as the time when the Mooney had increased by 5 Mooney points (t above the minimum Mooney, using a test temperature of 125C and the stress-strain properties were determined using ASTM procedures.

Comparison of the scorch times for experiments 1, 2 and 3 and for 4 and 5 and for 6 and 7 show that the addition of the calcium salt of the dimer of linoleic acid does cause an increase in the scorch time in different recipes. The stress-strain properties show that the presence of the scorch retarder does not detract from the properties of the vulcanizates.

TABLE I Calcium salt Scorch Experiment Benzothiazyl Magnesium of Dimer of Time Tensile 300% Elongation No. Disulphide Oxide Linoleic Acid t /l25C Strength Modulus g g g minutes Kg/cm Kg/cm 1 (Control) 0 0 0 6.62 106 54 560 3 O (l 2.2 957 I01 58 500 4 (Control) 0 1.1 0 7.02 100 58 500 6 (Control) LI 0 O 7.]8 Ill 5] 600 7 LI 0 L] 9.40 I15 47 (HO Bromobutyl 550 Natural rubber 185 St "d 7.3 (lir lit fn liliick 44 A compound identical with that of Example 1 was Paraffinic oil 110 prepared in a Banbury mixer. Into 1200 parts of this Tackifier resin 29 Zine oxide 3 Bcnzothiazyl disulphide Alkyl phenol disulphide parts by weight compound was mixed, using a rubber compounding mill, the following:

Zinc oxide 3 Benzothiazyl Disulphide Vultac 5 2.9 parts by weight 6.6 6.6

continued TABLE II Ex.- Scorchper- Time ment t,,/l25C No. Additive Minutes 1 Nil (Control) 6.97 2 Calcium salt of dimer of linoleic acid 10.75 3 Calcium salt of trimer of linoleic acid 11.9 4 Barium salt of dimer of linoleic acid 12.45 5 Barium salt of trimer of linoleic acid 15.5 6 Nil (Control) 6.37 7 Dimer of linoleic acid 8.87 8 Trimer of linoleic acid 9.0 9 Magnesium salt of dimer of linoleic acid 7.4 10 Magnesium salt of trimer of linoleic acid 10.41 1 1 Aluminum salt of dimer of linoleic acid 7.06 12 Aluminum salt of trimer of linoleic acid 7.45

The linoleic acid dimer and trimer were commercial products available from Emery Industries Ltd. as Empol Dimer 1,022 and Empol Trimer 1,040 respectively. The salts were prepared as described in Example 1.

EXAMPLE 3 Bromobutyl-containing compounds were prepared using the ingredients in Part A of Table III. The

bromobutyl had the bromine contents and Mooney as TABLE 111 PART A Experiment No. l 2 3 4 Bromohutyl 7 75 100 100 Wt of bromine of bromobutyl 1.9 1.65 1.9 1.65 Mooney of bromobutyl 44 43.5 44 43.5 Natural Rubber 25 25 General purpose furnace carbon black 62.5 62.5 62.5 62.5 Stearic acid 1 1 1 l Benzothiazyl disulphide 1.25 1.25 1.25 1.25 Paraffin oil 14 14 14 14 Tackifier resin 4 4 4 4 Dipentamethylene thiuram tetrasulphide 0.2 0.2 Zinc oxide 5 5 5 5 Sulphur 0.5 0.5 4.4'-Dithiomorpholine 0.15 0.15

PART 8 Calcium salt of linoleic acid dimer 0* 1 gram 0* 1 gram Scorch time t,-,/ 135C (minS.) 10.88 15.77 10.2 14.85

Control EXAMPLE 4 Using a Model B Banbury, a masterbatch was prepared of the following components, using the procedure of Example I, all parts being parts by weight.

Ethylcne-propylene-ethylidene norhornene po|ymer* I60 Bromobutyl 180 Styrene-hutadicnc ruhher 100 Natural rubber 360 Fast extruding furnace carbon black 400 Stearic acid 8 Light parafflnic oil 96 Paraffin wax *Royalenc 502, sold by United States Rubber Co.

lnto 1200 parts of this masterbatch were blended on a cool rubber compounding mill the following:

Zinc oxide 22 parts Sulphur 3.7 Benzothiazyl disulphide 5.5 Vultac S 9 This compound was divided into portions of 150g weight and to each portion was added the quantity shown in Table IV of the calcium salt of the dimer of linoleic acid and the scorch time was then determined on each sample.

, TABLE [.V

Quantity of Calcium Salt Scorch Time Experiof linoleic acid dimer t5/135C ment No. g'(phr) minutes *Control The effect on the scorch time of increasing the quantity of the scorch retarding agent in the compound can clearly be seen.

EXAMPLE 5 Using a mill mixing procedure a vulcanizable mixture was prepared using a sample of chlorobutyl as the rubber component, the contents of the mixture being as given in Table V. The mixture was divided into two equal portions, and to one portion was added 1 g of the calcium salt of the dimer of linoleic acid. The scorch time was determined for each portion of the mixture.

The chlorobutyl used had a chlorine content of 1.1 weight per cent and a Mooney (ML 1 4 at 125C) of 56. The presence of the calcium salt of the linoleic acid dimer clearly increases the scorch time of the vulcanizable mixture.

EXAMPLE 6 A compound of bromobutyl was prepared, using a mill mixing procedure, by mixing 200g of bromobutyl, 100g of a semi-reinforcing furnace carbon black, 2g of stearic acid and, as the curing agent, 10g of zinc oxide. The bromobutyl used had a Mooney of 45 and contained 1.9 weight per cent bromine. This compound y 7 served as a control. A second compound was prepared in exactly the same manner with the exception that lg of the calcium salt of the dimer of linoleic acid was added. The scorch time (L /135C) for the control compound was 10.5 minutes whereas that for the compound containing the scorch retarder of the invention was 1 1.7 minutes.

What is claimed is:

l. A vulcanizable composition having improved scorch characteristics which comprise (a) a polymeric component being a halogenated butyl rubber and at least one of natural rubber and synthetic unsaturated rubbers selected from polyisoprene, polybutadiene, styrene-butadiene polymers and ethylene-propylenediene polymers said halogenated butyl rubber forms at least weight percent of said polymeric component and (b) a scorch retarding agent selected from at least one of the free acid and the aluminum. barium, calcium and magnesium salts of an oligomer of linoleic acid, said scorch retarding agent being present in an amount from about 0.5 parts to about 5 parts by weight per 100 parts by weight of said polymeric component.

2. The composition of claim 1 in which the synthetic unsaturated rubber is a styrene-butadiene polymer.

3. The composition of claim 2 in which the synthetic unsaturated rubber is a styrene-butadiene polymer and an cthylene-propylene-diene polymer.

4. The composition of claim 2 in which the synthetic unsaturated rubber is a polybutadiene.

5. The composition of claim 1 in which said halogenated butyl rubber is selected from chlorobutyl and bromobutyl.

6. The composition of claim 5 in which said halogenated butyl rubber is a polymer containing, based on hydrocarbons, from 97 to 99.5 weight per cent of isobutylene and from 0.5 to 3 weight per cent of isoprene and, based on halogenated polymer, from 0.5 to 5 weight per cent of bromine.

7. The composition of claim 2 in which said halogenated butyl rubber is a polymer containing, based on hydrocarbons. from 97 to 99.5 weight per cent of isobutylene. and from 0.5 to 3 weight per cent of isoprene and, based on halogenated polymer, from 0.5 to 2 weight per cent of chlorine.

8. The composition of claim 5 in which said scorch retarding agent is the calcium salt of the dimer of linoleic acid present in an amount of from 0.75 to 2.5 parts by weight per parts by weight of polymeric component.

9. The composition of claim 5 in which said scorch retarding, agent is the calcium salt of the trimer of linoleic acid present in an amount of from 0.75 to 2.5 parts by weight per 100 parts by weight of polymeric component.

10. The composition of claim 5 in which said halogenated butyl rubber is a polymer containing, based on hydrocarbons, from 98 to 99 weight per cent of isobutylene and from I to 2 weight per cent of isoprene and, based on halogenated polymer, from 1.5 to 2.5 weight per cent of bromine, said halogenated butyl rubber forms at least 20 weight per cent of said polymeric component and said scorch retarding agent is the calcium salt of the dimer of linoleic acid present in an amount of from 0.75 to 2.5 parts by weight per 100 parts by weight of polymeric component. 

1. A VULCANIZABLE COMPOSITION HAVING IMPROVED SCORCH CHARACTERISTICS WHICH COMPRISE (A) A POLYMERIC COMPONENT BEING A HALOGENAED BUTYL RUBBER AND AT LEAST ONE OF NUTRAL RUBBER AND SYNTHETIC UNSATURATED RUBBERS SELECTED FROM POLYISOPRENE, POLYBUTADIENE, STYRENE-BUTADIENE POLYMERS AND ETHYLENE-PROPYLENE-DIENE POLYMERS SAID HALOGENATED BUTYL RUBBER FORMS AT LEAST 20 WEIGHT PERCENT OF SAID POLYMERIC COMPONENT AND (B) A SCORCH RETARDING AGENT SELECTED FROM AT LEAST ONE OF THE FREE ACID AND THE ALUMINUM, BARIUM, CALCIUM AND MAGNESIUM SALTS OF AN OLIGOMER OF LINOLEIC ACID, SAID SCORCH RETARDING AGENT BEING PRESENT IN AN AMOUNT FROM ABOUT 0.5 PARTS TO ABOUT 5 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF SAID POLYMERIC COMPONENT.
 2. The composition of claim 1 in which the synthetic unsaturated rubber is a styrene-butadiene polymer.
 3. The composition of claim 2 in which the synthetic unsaturated rubber is a styrene-butadiene polymer and an ethylene-propylene-diene polymer.
 4. The composition of claim 2 in which the synthetic unsaturated rubber is a polybutadiene.
 5. The composition of claim 1 in which said halogenated butyl rubber is selected from chlorobutyl and bromobutyl.
 6. The composition of claim 5 in which said halogenated butyl rubber is a polymer containing, based on hydrocarbons, from 97 to 99.5 weight per cent of isobutylene and from 0.5 to 3 weight per cent of isoprene and, based on halogenated polymer, from 0.5 to 5 weight per cent of bromine.
 7. The composition of claim 2 in which said halogenated butyl rubber is a polymer containing, based on hydrocarbons, from 97 to 99.5 weight per cent of isobutylene, and from 0.5 to 3 weight per cent of isoprene and, based on halogenated polymer, from 0.5 to 2 weight per cent of chlorine.
 8. The composition of claim 5 in which said scorch retarding agent is the calcium salt of the dimer of linoleic acid present in an amount of from 0.75 to 2.5 parts by weight per 100 parts by weight of polymeric component.
 9. The composition of claim 5 in which said scorch retarding agent is the calcium salt of the trimer of linoleic acid present in an amount of from 0.75 to 2.5 parts by weight per 100 parts by weight of polymeric component.
 10. The composition of claim 5 in which said halogenated butyl rubber is a polymer containing, based on hydrocarbons, from 98 to 99 weight per cent of isobutylene and from 1 to 2 weight per cent of isoprene and, based on halogenated polymer, from 1.5 to 2.5 weight per cent of bromine, said halogenated butyl rubber forms at least 20 weight per cent of said polymeric component and said scorch retarding agent is the calcium salt of the dimer of linoleic acid present in an amount of from 0.75 to 2.5 parts by weight per 100 parts by weight of polymeric component. 